Aluminum oxides, such as Al2O3, are dielectrics finding increasing use in the fabrication of integrated circuits. One such use is in the fabrication of capacitors, for example as might be used in the fabrication of logic circuitry, or memory circuitry such as DRAM. Further and regardless, it is sometimes desirable to etch an aluminum oxide comprising material selectively to other materials over a substrate, for example doped and updoped silicon dioxides, titanium nitride, hafnium nitride and aluminum nitride. In the context of this document, a “doped” silicon dioxide comprises silicon dioxide having at least 2 total atomic percent of one or both of phosphorus and boron doping, with an “undoped” silicon dioxide comprising less than 2 total atomic percent of one or both of phosphorus and boron doping, including 0% of such doping.
One example chemistry for etching aluminum oxide is a base-buffered HF solution (for example 100 volume parts water to 1 volume part HF to 15 volume parts of a base) to provide the primary H2F2 etching species. This exemplary chemistry provides very good selectivity in etching aluminum oxides relative to titanium nitride, for example a selectivity of about 500:1. In the context of this document, selectivity in an etch for etching one material selectively to another requires removal/etching of the one relative to the other at a ratio of at least 2:1. Of course, often much higher selectivities are obtainable and desirable. The above exemplary chemistry has not produced desired degree of selectivity in etching aluminum oxide selectively relative to hafnium nitride and aluminum nitride. For example, using the above chemistry not only etches aluminum oxide but also etches aluminum nitride and hafnium nitride just as fast or faster.
While the invention was motivated in addressing the above identified issues, it is in no way so limited. Rather, the invention is only limited by the accompanying claims as literally worded without interpretative or other limiting reference to the specification, and in accordance with the doctrine of equivalents.